A number of different packaging technologies exist for attaching semiconductor devices to a printed circuit board (PCB). Many of today's consumer electronic devices, such as personal video players, video games, and hand held computers require a high density of integrated circuits mounted on the PCB. The three packaging technologies include a ball grid array (BGA), chip scale package (CSP), and direct chip attach (DCA). BGA is an older technology relative to CSP and DCA. Theoretically speaking, the most effective packaging technology is DCA. DCA involves the direct attachment of the chip to the PCB without a package, such as a solder-bumped flip chip or wire bonding chip on the board. Issues with respect to the cost of supplying a known good die (KGD) and corresponding fine line and spacing PCB are present. As a result, CSP's and BGA's are the main types of packaging technology used in attaching semiconductors to PCB's.
As the demand for high speed, high performance, and low cost, semiconductor devices are continually increasing in integration density, packages have become more complex. For example, packages are present in which multiple chips are placed within a single package. These types of chips are also referred to as multi-chip modules. A multi-chip module (MCM), also referred to as a multi-chip package (MCP), contains two or more die in a single package. These multi-chip modules may contain microprocessor circuits along with peripheral circuits, such as memory management units, input/output controllers, peripheral component interconnect or interface (PCI) controllers, and application specific integrated circuits (ASIC).
In the integrated circuit world, high performance translates to high heat. This presents an additional problem that may become critical to the reliability of the package. By packaging multiple semiconductor devices in a single package the heating problem becomes more daunting.
The most common MCM is a “side-by-side” MCM. In this type of MCM, two or more die are mounted next to each other on the mounting surface of either a plastic molded package, cavity package, or a chip on board (COB) assembly. The die may be mounted directly to the mounting surface or be mounted on a substrate, which is itself mounted to the principle-mounting surface. Inner connections among these die and electrical leads are commonly made via wire bonding. Other MCM's involve placing two or more die on top of each other and securing the “stack” of die in a package. This may add additional reliability concerns as the upper die in the stack may be heated by the lower die.
One problem with placing multiple die within a single package is with additional die, additional possible defects are possible within the package. If one die within an MCM is defective, the entire chip must then be discarded. Thus, although MCM's have provided increased functionality, yields have decreased as a result of the increased chances for defects.
Thus, a need still remains for a ball grid array package stacking system. In view of the increasing demand for more circuit function in limited space, it is increasingly critical that answers be found to these problems. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to save costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.